DOCSLIB.ORG

High-Resolution Measurements of the Dark Matter Halo of NGC 2976

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
High-Resolution Measurements of the Dark Matter Halo of NGC 2976 Accepted for publication in The Astrophysical Journal A Preprint typeset using L TEX style emulateapj v. 11/12/01 HIGH-RESOLUTION MEASUREMENTS OF THE DARK MATTER HALO OF NGC 2976: EVIDENCE FOR A SHALLOW DENSITY PROFILE1 Joshua D. Simon2, Alberto D. Bolatto2, Adam Leroy2, and Leo Blitz Department of Astronomy, University of California at Berkeley 601 Campbell Hall, CA 94720 [email protected], [email protected], [email protected], [email protected] Accepted for publication in The Astrophysical Journal ABSTRACT We have obtained two-dimensional velocity fields of the dwarf spiral galaxy NGC 2976 in Hα and CO. The high spatial (∼ 75 pc) and spectral (13 km s−1 and 2 km s−1, respectively) resolution of these observations, along with our multicolor optical and near-infrared imaging, allow us to measure the shape of the density profile of the dark matter halo with good precision. We find that the total −0.27±0.09 (baryonic plus dark matter) mass distribution of NGC 2976 follows a ρTOT ∝ r power law out to a radius of 1.8 kpc, assuming that the observed radial motions provide no support. The density profile attributed to the dark halo is even shallower, consistent with a nearly constant density of dark matter over the entire observed region. A maximal disk fit yields an upper limit to the K-band stellar mass-to- +0.15 light ratio (M∗/LK) of0.09−0.08M⊙/L⊙K (including systematic uncertainties), with the caveat that for M∗/LK > 0.19M⊙/L⊙K the dark matter density increases with radius, which is unphysical. Assuming −0.17 0.10M⊙/L⊙K . M∗/LK ≤ 0.19M⊙/L⊙K, the dark matter density profile lies between ρDM ∝ r and −0.01 ρDM ∝ r . Therefore, independent of any assumptions about the stellar disk or the functional form of the density profile, NGC 2976 does not contain a cuspy dark matter halo. We also investigate some of the systematic effects that can hamper rotation curve studies, and show that 1) longslit rotation curves are far more vulnerable to systematic errors than two-dimensional velocity fields, 2) NGC 2976 contains radial motions that are as large as 90 % of the rotational velocities at small radii, and 3) the Hα and CO velocity fields of NGC 2976 agree within their uncertainties, with a typical scatter between the two velocities of 5.3 km s−1 at any position in the galaxy. Subject headings: dark matter — galaxies: dwarf — galaxies: individual (NGC 2552; NGC 2976) — galaxies: kinematics and dynamics — galaxies: spiral 1. introduction latto et al. (2002) showed that NGC 4605 has a density profile ρ ∝ r−0.65, and Weldrake et al. (2003) determined The apparent disagreement between the observed dark matter density profiles of dwarf and low-surface brightness that NGC 6822 contains an essentially constant-density (LSB) galaxies and the density profiles predicted by nu- halo. The recent study by SMVB shows that, in large part, merical Cold Dark Matter (CDM) simulations has been widely discussed by both theorists and observers over the the lack of consensus among observers reflects ambigui- ties in the data themselves. For the parameters of typical past several years (e.g., Flores & Primack 1994; Burkert −1 arXiv:astro-ph/0307154v1 8 Jul 2003 dwarf/LSB galaxy observations (∼ 50 km s velocity res- 1995; Navarro, Frenk, & White 1996; Moore et al. 1999b). ∼ ′′ However, there remains a disturbing lack of consensus in olution and 1 seeing for longslit Hα observations, and ∼ −1 ∼ ′′ the observational community on the actual shape of the ob- 2 km s velocity resolution and 15 angular resolu- tion for H I interferometry), they find that most galaxies served dark matter density profiles. Many authors claim show central density profiles that are consistent with any that only constant-density cores are allowed by the obser- shape between 0 and −1. vations (de Blok et al. 2001; Borriello & Salucci 2001; de r r We address this problem with a new study that com- Blok, McGaugh, & Rubin 2001; de Blok & Bosma 2002; Salucci, Walter, & Borriello 2002; Weldrake, de Blok, & bines a number of techniques to overcome the obser- vational challenges. Our program includes 1) two- Walter 2003). On the other hand, van den Bosch et al. dimensional velocity fields obtained at optical (Hα), mil- (2000), van den Bosch & Swaters (2001), and Swaters et limeter (CO), and centimeter (H I) wavelengths, 2) high al. (2002, hereafter SMVB) argue that most existing ro- ′′ − angular resolution (∼ 5 ), 3) high spectral resolution tation curves are also consistent with NFW-like (ρ ∝ r 1) (. 10 km s−1), 4) multicolor optical and near-infrared central density cusps. Even the very highest resolution (. 100 pc) studies do not seem to be converging on a single photometry, and 5) nearby dwarf galaxies as targets. Ob- serving completely independent tracers of the velocity field result; Blais-Ouellette, Amram, & Carignan (2001) found − − at two or three different wavelengths reduces our vulner- ρ ∝ r 0.3 in NGC 3109 and ρ ∝ r 0.5 in IC 2574 (ignoring the stellar disk contributions to the rotation curves), Bo- ability to the systematic problems that can affect a single tracer. For example, Hα velocity fields can be distorted 1 Based on observations carried out at the WIYN Observatory. The WIYN Observatory is a joint facility of the University of Wisconsin-Madison, Indiana University, Yale University, and the National Optical Astronomy Observatory. 2 Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation. 1 2 Simon et al. by extinction, or by large-scale flows that are associated combined with archival 2MASS near-infrared images, en- with star formation, while existing H I data generally suf- ables us to accurately model the stellar disk. fer from beam smearing. Two-dimensional velocity fields In the following section, we describe NGC 2976 and our also represent a major improvement over the traditional observations and data reduction. In §3, we model the stel- longslit spectra, making the effect of positioning errors lar and gaseous disks. In §4, we derive the rotation curve negligible and allowing us to account for simple noncircu- of the galaxy and the density profile of its dark matter lar motions. High angular resolution is important because halo. The analysis routines that we use are presented in the central cores described in the literature have typical more detail in Appendix A. We discuss our results and radii of ∼ 1 kpc, which corresponds to an angular size of their implications in §5. In §6, we describe some system- 20.6(d/10Mpc)−1 arcseconds. In order to resolve this size atic uncertainties that can affect rotation curve studies, scale and minimize the impact of beam smearing on our and test the robustness of our results against them. We conclusions, an angular resolution element several times present our conclusions in §7. smaller is required. High spectral resolution is also bene- ficial because it results in more accurate rotation curves. 2. target, observations, and data reduction Finally, our multicolor photometry plays a crucial role in allowing us to attempt to realistically model the rotational 2.1. Properties of NGC 2976 contribution from stellar disks instead of simply guessing NGC 2976 is a regular Sc dwarf galaxy located in the an appropriate mass-to-light ratio and assuming an expo- M 81 group. Karachentsev et al. (2002) measured a dis- nential disk. tance of 3.56 ± 0.38 Mpc using the Tip of the Red Giant Target selection also has important effects on the Branch (TRGB) method, and the Tully-Fisher distance is strength of the conclusions we will be able to draw. We fo- 3.33 ± 0.50 Mpc (M. Pierce, private communication). We cus on very nearby objects (D < 10 Mpc) in order to max- adopt a distance of 3.45 Mpc, which sets the conversion imize our physical resolution. Dwarf and LSB galaxies are between physical and angular scales to 16.7 pc arcsec−1. the preferred targets for this type of study because they are NGC 2976 has absolute magnitudes of MB = −17.0 and −1 presumed to be the most dark-matter dominated galaxies. MK = −20.2, a heliocentric velocity of −0.8 ± 1.8km s , −1 (Note that in this paper when we refer to dwarf galaxies, an inclination-corrected H I linewidth W20 =165 km s , 9 we mean high-mass dwarf irregulars and low-mass spiral and a total mass of 3.5 × 10 M⊙, so it is somewhat less lu- galaxies, not dwarf spheroidals or ellipticals.) LSB galax- minous and less massive than the Large Magellanic Cloud. ies, though, tend to be relatively distant and are necessar- The low systemic velocity is not a problem for our obser- ily quite faint, so they are difficult to observe with suffi- vations because the galaxy is located at high Galactic lat- cient resolution and sensitivity. Dwarf galaxies, in compar- itude, where there is little Milky Way CO emission, and ison, are both bright and plentiful in the nearby universe. no Galactic Hα emission is visible. In optical and near- Dwarfs are traditionally presumed to be dark-matter dom- infrared images it is clear that NGC 2976 is a bulgeless, inated at all radii (Carignan & Freeman 1988; Carignan unbarred, pure disk system (see Figure 1), which makes it & Beaulieu 1989; Jobin & Carignan 1990; Martimbeau, an ideal galaxy for mass modeling. Carignan, & Roy 1994). However, the observations upon which this assumption is based were made at low angu- 2.2.
Load more

Recommended publications
  • The Local Galaxy Volume
    11-1 How Far Away Is It – The Local Galaxy Volume The Local Galaxy Volume {Abstract – In this segment of our “How far away is it” video book, we cover the local galaxy volume compiled by the Spitzer Local Volume Legacy Survey team. The survey covered 258 galaxies within 36 million light years. We take a look at just a few of them including: Dwingeloo 1, NGC 4214, Centaurus A, NGC 5128 Jets, NGC 1569, majestic M81, Holmberg IX, M82, NGC 2976,the unusual Circinus, M83, NGC 2787, the Pinwheel Galaxy M101, the Sombrero Galaxy M104 including Spitzer’s infrared view, NGC 1512, the Whirlpool Galaxy M51, M74, M66, and M96. We end with a look at the tuning fork diagram created by Edwin Hubble with its description of spiral, elliptical, lenticular and irregular galaxies.} Introduction [Music: Johann Pachelbel – “Canon in D” – This is Pachelbel's most famous composition. It was written in the 1680s between the times of Galileo and Newton. The term 'canon' originates from the Greek kanon, which literally means "ruler" or "a measuring stick." In music, this refers to timing. In astronomy, "a measuring stick" refers to distance. We now proceed to galaxies more distant than the ones in our Local Group.] The Local volume is the set of galaxies covered in the Local Volume Legacy survey or LVL, for short, conducted by the Spitzer team. It is a complete sample of 258 galaxies within 36 million light years. This montage of images shows the ensemble of galaxies as observed by Spitzer. The galaxies are randomly arranged but their relative sizes are as they appear on the sky.
    [Show full text]
  • 1. Introduction
    THE ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 122:109È150, 1999 May ( 1999. The American Astronomical Society. All rights reserved. Printed in U.S.A. GALAXY STRUCTURAL PARAMETERS: STAR FORMATION RATE AND EVOLUTION WITH REDSHIFT M. TAKAMIYA1,2 Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637; and Gemini 8 m Telescopes Project, 670 North Aohoku Place, Hilo, HI 96720 Received 1998 August 4; accepted 1998 December 21 ABSTRACT The evolution of the structure of galaxies as a function of redshift is investigated using two param- eters: the metric radius of the galaxy(Rg) and the power at high spatial frequencies in the disk of the galaxy (s). A direct comparison is made between nearby (z D 0) and distant(0.2 [ z [ 1) galaxies by following a Ðxed range in rest frame wavelengths. The data of the nearby galaxies comprise 136 broad- band images at D4500A observed with the 0.9 m telescope at Kitt Peak National Observatory (23 galaxies) and selected from the catalog of digital images of Frei et al. (113 galaxies). The high-redshift sample comprises 94 galaxies selected from the Hubble Deep Field (HDF) observations with the Hubble Space Telescope using the Wide Field Planetary Camera 2 in four broad bands that range between D3000 and D9000A (Williams et al.). The radius is measured from the intensity proÐle of the galaxy using the formulation of Petrosian, and it is argued to be a metric radius that should not depend very strongly on the angular resolution and limiting surface brightness level of the imaging data. It is found that the metric radii of nearby and distant galaxies are comparable to each other.
    [Show full text]
  • Spiral Galaxy HI Models, Rotation Curves and Kinematic Classifications
    Spiral galaxy HI models, rotation curves and kinematic classifications Theresa B. V. Wiegert A thesis submitted to the Faculty of Graduate Studies of The University of Manitoba in partial fulfillment of the requirements of the degree of Doctor of Philosophy Department of Physics & Astronomy University of Manitoba Winnipeg, Canada 2010 Copyright (c) 2010 by Theresa B. V. Wiegert Abstract Although galaxy interactions cause dramatic changes, galaxies also continue to form stars and evolve when they are isolated. The dark matter (DM) halo may influence this evolu- tion since it generates the rotational behaviour of galactic disks which could affect local conditions in the gas. Therefore we study neutral hydrogen kinematics of non-interacting, nearby spiral galaxies, characterising their rotation curves (RC) which probe the DM halo; delineating kinematic classes of galaxies; and investigating relations between these classes and galaxy properties such as disk size and star formation rate (SFR). To generate the RCs, we use GalAPAGOS (by J. Fiege). My role was to test and help drive the development of this software, which employs a powerful genetic algorithm, con- straining 23 parameters while using the full 3D data cube as input. The RC is here simply described by a tanh-based function which adequately traces the global RC behaviour. Ex- tensive testing on artificial galaxies show that the kinematic properties of galaxies with inclination > 40 ◦, including edge-on galaxies, are found reliably. Using a hierarchical clustering algorithm on parametrised RCs from 79 galaxies culled from literature generates a preliminary scheme consisting of five classes. These are based on three parameters: maximum rotational velocity, turnover radius and outer slope of the RC.
    [Show full text]
  • April Constellations of the Month
    April Constellations of the Month Leo Small Scope Objects: Name R.A. Decl. Details M65! A large, bright Sa/Sb spiral galaxy. 7.8 x 1.6 arc minutes, magnitude 10.2. Very 11hr 18.9m +13° 05’ (NGC 3623) high surface brighness showing good detail in medium sized ‘scopes. M66! Another bright Sb galaxy, only 21 arc minutes from M65. Slightly brighter at mag. 11hr 20.2m +12° 59’ (NGC 3627) 9.7, measuring 8.0 x 2.5 arc minutes. M95 An easy SBb barred spiral, 4 x 3 arc minutes in size. Magnitude 10.5, with 10hr 44.0m +11° 42’ a bright central core. The bar and outer ring of material will require larger (NGC 3351) aperature and dark skies. M96 Another bright Sb spiral, about 42 arc minutes east of M95, but larger and 10hr 46.8m +11° 49’ (NGC 3368) brighter. 6 x 4 arc minutes, magnitude 10.1. Located about 48 arc minutes NNE of M96. This small elliptical galaxy measures M105 only 2 x 2.1 arc minutes, but at mag. 10.3 has very high surface brightness. 10hr 47.8m +12° 35’ (NGC 3379) Look for NGC 3384! (110NGC) and NGC 3389 (mag 11.0 and 12.2) which form a small triangle with M105. NGC 3384! 10hr 48.3m +12° 38’ See comment for M105. The brightest galaxy in Leo, this Sb/Sc spiral galaxy shines at mag. 9.5. Look for NGC 2903!! 09hr 32.2m +21° 30’ a hazy patch 11 x 4.7 arc minutes in size 1.5° south of l Leonis.
    [Show full text]
  • Galaxies and Cosmology (2011)
    Galaxien und Kosmologie / Galaxies and Cosmology (2011) Refereed Papers Adams, J. J., K. Gebhardt, G. A. Blanc, M. H. Fabricius, G. J. Hill, J. D. Murphy, R. C. E. van den Bosch and G. van de Ven: The central dark matter distribution of NGC 2976. The Astrophysical Journal 745, id. 92 (2011) Aihara, H., C. Allende Prieto, D. An, S. F. Anderson, É. Aubourg, E. Balbinot, T. C. Beers, A. A. Berlind, S. J. Bickerton, D. Bizyaev, M. R. Blanton, J. J. Bochanski, A. S. Bolton, J. Bovy, W. N. Brandt, J. Brinkmann, P. J. Brown, J. R. Brownstein, N. G. Busca, H. Campbell, M. A. Carr, Y. Chen, C. Chiappini, J. Comparat, N. Connolly, M. Cortes, R. A. C. Croft, A. J. Cuesta, L. N. da Costa, J. R. A. Davenport, K. Dawson, S. Dhital, A. Ealet, G. L. Ebelke, E. M. Edmondson, D. J. Eisenstein, S. Escoffier, M. Esposito, M. L. Evans, X. Fan, B. Femenía Castellá, A. Font-Ribera, P. M. Frinchaboy, J. Ge, B. A. Gillespie, G. Gilmore, J. I. González Hernández, J. R. Gott, A. Gould, E. K. Grebel, J. E. Gunn, J.-C. Hamilton, P. Harding, D. W. Harris, S. L. Hawley, F. R. Hearty, S. Ho, D. W. Hogg, J. A. Holtzman, K. Honscheid, N. Inada, I. I. Ivans, L. Jiang, J. A. Johnson, C. Jordan, W. P. Jordan, E. A. Kazin, D. Kirkby, M. A. Klaene, G. R. Knapp, J.-P. Kneib, C. S. Kochanek, L. Koesterke, J. A. Kollmeier, R. G. Kron, H. Lampeitl, D. Lang, J.-M. Le Goff, Y.
    [Show full text]
  • Astronomy Magazine Special Issue
    γ ι ζ γ δ α κ β κ ε γ β ρ ε ζ υ α φ ψ ω χ α π χ φ γ ω ο ι δ κ α ξ υ λ τ μ β α σ θ ε β σ δ γ ψ λ ω σ η ν θ Aι must-have for all stargazers η δ μ NEW EDITION! ζ λ β ε η κ NGC 6664 NGC 6539 ε τ μ NGC 6712 α υ δ ζ M26 ν NGC 6649 ψ Struve 2325 ζ ξ ATLAS χ α NGC 6604 ξ ο ν ν SCUTUM M16 of the γ SERP β NGC 6605 γ V450 ξ η υ η NGC 6645 M17 φ θ M18 ζ ρ ρ1 π Barnard 92 ο χ σ M25 M24 STARS M23 ν β κ All-in-one introduction ALL NEW MAPS WITH: to the night sky 42,000 more stars (87,000 plotted down to magnitude 8.5) AND 150+ more deep-sky objects (more than 1,200 total) The Eagle Nebula (M16) combines a dark nebula and a star cluster. In 100+ this intense region of star formation, “pillars” form at the boundaries spectacular between hot and cold gas. You’ll find this object on Map 14, a celestial portion of which lies above. photos PLUS: How to observe star clusters, nebulae, and galaxies AS2-CV0610.indd 1 6/10/10 4:17 PM NEW EDITION! AtlAs Tour the night sky of the The staff of Astronomy magazine decided to This atlas presents produce its first star atlas in 2006.
    [Show full text]
  • The Professor Comet's Report Early Spring – April 2012
    The Professor Comet’s Report 1 Mr. Justin J McCollum (BS, MS Physics) Lab Physics Coordinator Dept. of Physics Lamar University Welcome to the comet report which is a monthly article on the observations of comets by the amateur astronomy community and comet hunters from around the world! This C/2009 P1 Garradd with article is dedicated to the latest reports of available comets for Barred Spiral Galaxy NGC 4236 observations, current state of those comets, future 14 March 2011! predictions, & projections for observations in comet astronomy! Early Spring – April 2012 The Professor Comet’s Report 2 The Current Status of the Predominant Comets for Apr 2012! Comets Designation Orbital Magnitude Trend Observation Constellations Visibility (IAU – MPC) Status Visual (Range in (Night Sky Location) Period Lat.) Garradd 2009 P1 C 7.0* - 7.5 Fading 90°N – 30°S SW region of Ursa Major moving All Night SSW towards the SE region of Lynx. Giacobini - 21P P 9 – 10 Fading Poor N/A Zinner Elongation Lost in the daytime Glare! LINEAR 2011 F1 C 11 .7* Brightening 90°N – 20°S Undergoing retrograde motion All Night between Boötes and Draco thru the late Spring. Gehrels 2 78P P 12.2* Fading 60˚N - 20˚S Moving eastwards across Taurus Early Evening and progressing along the N edge of the Hyades Star Cluster! McNaught 2011 Q2 C 12.5 Fading 70˚N – Eqn. Currently in the S central region Early Morning of Andromeda moving NE between the boundary between Andromeda & Pisces. NEAT 246P/2010 V2 P 12.3* - 13 Possible 65˚N - 60˚S Undergoing retrograde motion All Night Steadiness in the E half of the N central region of Virgo until late June.
    [Show full text]
  • Strong Evidence for the Density-Wave Theory of Spiral Structure from a Multi-Wavelength Study of Disk Galaxies Hamed Pour-Imani University of Arkansas, Fayetteville
    University of Arkansas, Fayetteville ScholarWorks@UARK Theses and Dissertations 8-2018 Strong Evidence for the Density-wave Theory of Spiral Structure from a Multi-wavelength Study of Disk Galaxies Hamed Pour-Imani University of Arkansas, Fayetteville Follow this and additional works at: http://scholarworks.uark.edu/etd Part of the Physical Processes Commons, and the Stars, Interstellar Medium and the Galaxy Commons Recommended Citation Pour-Imani, Hamed, "Strong Evidence for the Density-wave Theory of Spiral Structure from a Multi-wavelength Study of Disk Galaxies" (2018). Theses and Dissertations. 2864. http://scholarworks.uark.edu/etd/2864 This Dissertation is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of ScholarWorks@UARK. For more information, please contact [email protected], [email protected]. Strong Evidence for the Density-wave Theory of Spiral Structure from a Multi-wavelength Study of Disk Galaxies A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Physics by Hamed Pour-Imani University of Isfahan Bachelor of Science in Physics, 2004 University of Arkansas Master of Science in Physics, 2016 August 2018 University of Arkansas This dissertation is approved for recommendation to the Graduate Council. Daniel Kennefick, Ph.D. Dissertation Director Vincent Chevrier, Ph.D. Claud Lacy, Ph.D. Committee Member Committee Member Julia Kennefick, Ph.D. William Oliver, Ph.D. Committee Member Committee Member ABSTRACT The density-wave theory of spiral structure, though first proposed as long ago as the mid-1960s by C.C.
    [Show full text]
  • Dwarf Galaxy Dark Matter Density Profiles Inferred from Stellar and Gas Kinematics
    ACCEPTED BY APJ Preprint typeset using LATEX style emulateapj v. 5/2/11 DWARF GALAXY DARK MATTER DENSITY PROFILES INFERRED FROM STELLAR AND GAS KINEMATICS* JOSHUA J. ADAMS1,2 , JOSHUA D. SIMON1, MAXIMILIAN H. FABRICIUS3,REMCO C. E. VAN DEN BOSCH4 , JOHN C. BARENTINE5, RALF BENDER3,6,KARL GEBHARDT5,7,GARY J. HILL 5,7,8 , JEREMY D. MURPHY9 ,R.A.SWATERS10, JENS THOMAS3,GLENN VAN DE VEN4, Accepted by ApJ ABSTRACT We present new constraints on the density profiles of dark matter (DM) halos in seven nearby dwarf galaxies from measurements of their integrated stellar light and gas kinematics. The gas kinematics of low mass galaxies frequently suggest that they contain constant density DM cores, while N-body simulations instead predict a cuspy profile. We present a data set of high resolution integral field spectroscopy on seven galaxies and measure the stellar and gas kinematics simultaneously. Using Jeans modeling on our full sample, we examine whether gas kinematics in general produce shallower density profiles than are derived from the stars. Although 2/7 galaxies show some localized differences in their rotation curves between the two tracers, estimates of the central logarithmic slope of the DM density profile, γ, are generally robust. The mean and standard deviation of the logarithmic slope for the population are γ = 0.67 0.10 when measured in the stars and γ = 0.58 0.24 when measured in the gas. We also find that the halos± are not under-concentrated at the radii of half± their maximum velocities. Finally, we search for correlations of the DM density profile with stellar velocity anisotropy and other baryonic properties.
    [Show full text]
  • Classification of Galaxies Using Fractal Dimensions
    UNLV Retrospective Theses & Dissertations 1-1-1999 Classification of galaxies using fractal dimensions Sandip G Thanki University of Nevada, Las Vegas Follow this and additional works at: https://digitalscholarship.unlv.edu/rtds Repository Citation Thanki, Sandip G, "Classification of galaxies using fractal dimensions" (1999). UNLV Retrospective Theses & Dissertations. 1050. http://dx.doi.org/10.25669/8msa-x9b8 This Thesis is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. This Thesis has been accepted for inclusion in UNLV Retrospective Theses & Dissertations by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted.
    [Show full text]
  • Arxiv:0907.4718V1 [Astro-Ph.GA] 27 Jul 2009 Nnab Aais Hi Ihlmnste ( Luminosities High Their Objects Point-Like Galaxies
    Submitted to Astrophysical Journal A Preprint typeset using L TEX style emulateapj v. 04/03/99 ULTRALUMINOUS X-RAY SOURCE CORRELATIONS WITH STAR-FORMING REGIONS Douglas A. Swartz1 Allyn F. Tennant2, and Roberto Soria3 Submitted to Astrophysical Journal ABSTRACT Maps of low-inclination nearby galaxies in Sloan Digitized Sky Survey u − g, g − r and r − i colors are used to determine whether Ultraluminous X-ray sources (ULXs) are predominantly associated with star-forming regions of their host galaxies. An empirical selection criterion is derived from colors of H ii regions in M 81 and M 101 that differentiates between the young, blue stellar component and the older disk and bulge population. This criterion is applied to a sample of 58 galaxies of Hubble type S0 and later and verified through an application of Fisher’s linear discriminant analysis. It is found that 60% (49%) of ULXs in optically-bright environments are within regions blueward of their host galaxy’s H ii regions compared to only 27% (0%) of a control sample according to the empirical (Fisher) criterion. This is an excess of 3σ above the 32% (27%) expected if the ULXs were randomly distributed within their galactic hosts. This indicates a ULX preference for young, ∼<10 Myr, OB associations. However, none of the ULX environments have the morphology and optical brightness suggestive of a massive young super star cluster though several are in extended or crowded star-forming (blue) environments that may contain clusters unresolved by Sloan imaging. Ten of the 12 ULX candidates with estimated X-ray luminosities in excess of 3×1039 ergs s−1 are equally divided among the group of ULX environments redward of H ii regions and the group of optically faint regions.
    [Show full text]
  • SAC's 110 Best of the NGC
    SAC's 110 Best of the NGC by Paul Dickson Version: 1.4 | March 26, 1997 Copyright °c 1996, by Paul Dickson. All rights reserved If you purchased this book from Paul Dickson directly, please ignore this form. I already have most of this information. Why Should You Register This Book? Please register your copy of this book. I have done two book, SAC's 110 Best of the NGC and the Messier Logbook. In the works for late 1997 is a four volume set for the Herschel 400. q I am a beginner and I bought this book to get start with deep-sky observing. q I am an intermediate observer. I bought this book to observe these objects again. q I am an advance observer. I bought this book to add to my collect and/or re-observe these objects again. The book I'm registering is: q SAC's 110 Best of the NGC q Messier Logbook q I would like to purchase a copy of Herschel 400 book when it becomes available. Club Name: __________________________________________ Your Name: __________________________________________ Address: ____________________________________________ City: __________________ State: ____ Zip Code: _________ Mail this to: or E-mail it to: Paul Dickson 7714 N 36th Ave [email protected] Phoenix, AZ 85051-6401 After Observing the Messier Catalog, Try this Observing List: SAC's 110 Best of the NGC [email protected] http://www.seds.org/pub/info/newsletters/sacnews/html/sac.110.best.ngc.html SAC's 110 Best of the NGC is an observing list of some of the best objects after those in the Messier Catalog.
    [Show full text]